This invention relates to making a tire mold by spraying molten atomized metal on a model to form a shell and then reinforcing the shell with a resin backing to form a mold segment for the tire mold. It has been found that this method of making a mold segment is much faster than the conventional methods of casting and machining mold segments. The time saved is particularly important when molds are needed for new tread designs which need to be road tested.
Heretofore a tread segment for a tire mold has been made by spraying low temperature atomized metal over a tread segment pattern to form a shell having the same configuration as the pattern. The shell was then provided with a backing of resin filler or other suitable material to support the shell before the pattern was removed. It has been found that in making of tire molds by this method there are problems which are not encountered in making molds for other purposes. For instance in spraying several layers of metal on the tread pattern to build up a laminated shell, there have been problems with cracking of the shell. Difficulties have also been experienced in fitting the segments together to provide a full circle tread molding surface. Also in order to provide the necessary heat conductivity of the mold segments, it has been desirable to mix metal granules in the heated resin. Air and other gases in the hot resin must be removed during injection of the resin into a shoe containing the shell and pattern. It has also been found that there is an optimum size shoe for each tire mold size. Making special size shoes for each size mold segment is not only expensive but time consuming. Another problem in making mold segments is providing venting so that there will be adequate removal of gases from the finished tire mold during vulcanization of tires.